1. Field of the Invention
The present invention relates to fuel injection systems for internal combustion engines, and more particularly to a starting control for fuel injected compression ignition engines such as diesel engines.
2. History of the Prior Art
It is well known to provide a fuel injected diesel engine in which fuel is injected into the engine by an injection pump controlled in part by a governor which operates at a speed determined by the speed of the engine and which varies the quantity of fuel injected by an interconnecting control rack. A speed control lever determines the basic speed of the engine by varying the tension on a tensioning lever via a main governor spring. The resulting tension on the tensioning lever exerted by the spring counters the opposing force of flyweights within the governor. A floating lever within the fuel injection system assumes a position as determined by the tensioning lever to position the control rack accordingly and thereby adjust the amount of fuel injected into the engine. When the desired speed is obtained, the flyweight assembly counterbalances the tensioning lever to fix the position of the control rack and stabilize the amount of fuel injected.
For starting, the speed control lever is moved all the way to one extreme. The flyweight assembly offers no resistance, and the main governor spring and the starting spring pull the tensioning lever and the floating lever into extreme positions to move the control rack into a starting fuel position. While the starter is cranking the engine, the injection pump beings supplying fuel to the engine. Once the engine has started the flyweight assembly overcomes the starter spring and the control rack moves back to a position where the forces on the flyweight and the governor spring are balanced.
It is well established that engine geometry including bore size, connecting rod length to crankshaft throw ratio, compression ratio, valve timing, combustion bowl geometry, nozzle location, nozzle orifice size and angles all influence the startability of diesel engines. All of these factors are for the most part determined by considerations other than starting and cannot be conveniently varied during starting. In addition, the timing, the rate and the quantity of fuel which is injected into the combustion chamber during starting have a very important influence. Unfortunately, these factors typically cannot be optimized for both starting and operation at normal running speeds. Consequently, such factors are normally optimized for normal operation of the engine at some sacrifice in the startability of the engine.
It would be desirable to provide a fuel injected compression ignition engine in which the performance of the fuel injection system is optimized for both starting and running at normal speeds.
It would furthermore be desirable to provide a fuel injected diesel engine which is relatively easy to start at varying temperatures and which at the same time runs smoothly and efficiently once started. Any controls added to the fuel injection system should preferably not interfere with the normal operation of the fuel injection system after the engine is started and running.